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Faster, More Awesome GitHub Pages

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Re: Faster, More Awesome GitHub Pages

#11

Post by namecast »

Interesting how ALIAS records are becoming a de-facto DNS protocol feature. Despite not having even an RFC draft proposing their existence, GitHub recommends using ALIAS records, and large players (e.g. AWS, Dyn, and DNSSimple IIRC, as well as us) now support adding ALIAS records to a domain.

I wonder why ALIAS took hold but DNAME and ANAME records were never widely supported despite actually making it into a few RFCs. Hrmm.

(Disclaimer: Namecast (http://www.namecast.net) supports ALIAS records as well, so I have an abnormal interest in what was otherwise a small part of the article.)

Re: Faster, More Awesome GitHub Pages

#13

Post by tedivm »

philip1209 wrote: post #4
pbreit wrote: post #2

What CDN? CloudFlare?

Doesn't look like it: dig +short NS github.io ns2.p16.dynect.net. ns4.p16.dynect.net. ns1.p16.dynect.net. ns3.p16.dynect.net.

All that shows is who they're hosting their DNS with, it has nothing to do with using a CDN. Dynect offers a CDN management tool that makes it easy to balance multiple CDNs across specific regions, so I'm not at all surprised they're using them for their DNS.

Re: Faster, More Awesome GitHub Pages

#14

Post by giovannibajo1 »

namecast wrote: post #11

Interesting how ALIAS records are becoming a de-facto DNS protocol feature. Despite not having even an RFC draft proposing their existence, GitHub recommends using ALIAS records, and large players (e.g. AWS, Dyn, and DNSSimple IIRC, as well as us) now support adding ALIAS records to a domain. I wonder why ALIAS took hold but DNAME and ANAME records were never widely supported despite actually making it into a few RFC…

The worst part of ALIAS is that traditional hosted DNS servers don't support it, as far as I can see. Usually CDN providers do handle static IP addresses at the zone apex somehow, but in this case it seems they don't.

Re: Faster, More Awesome GitHub Pages

#15

Post by chc »

harryh wrote: post #12

What's an ALIAS record? I don't even see that here: https://en.wikipedia.org/wiki/List_of_DNS_record_types

To my understanding, it's a new, nonstandard thing invented by DNSimple that lets you specify your base domain as a reference to another domain — basically, it's like a CNAME where an A record would normally be required.

Re: Faster, More Awesome GitHub Pages

#16

Post by sharth »

harryh wrote: post #12

What's an ALIAS record? I don't even see that here: https://en.wikipedia.org/wiki/List_of_DNS_record_types

Generally speaking, an ALIAS record points to a hostname. The DNS server software then fetches the IP address behind that hostname, and returns it as an A record to the user.

Normally, this is solved by using a CNAME record, but if you use a CNAME as the zone apex, then you cannot have any subdomains (because they will all be resolved through the CNAME record).

For some additional information: http://scripting.com/stories/2011/11/13/dnsimplesNewAliasFea... http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/Cre...

Re: Faster, More Awesome GitHub Pages

#17

Post by joaomsa »

namecast wrote: post #11

Interesting how ALIAS records are becoming a de-facto DNS protocol feature. Despite not having even an RFC draft proposing their existence, GitHub recommends using ALIAS records, and large players (e.g. AWS, Dyn, and DNSSimple IIRC, as well as us) now support adding ALIAS records to a domain. I wonder why ALIAS took hold but DNAME and ANAME records were never widely supported despite actually making it into a few RFC…

No support for ALIAS on namecheap

Re: Faster, More Awesome GitHub Pages

#18

Post by philip1209 »

tedivm wrote: post #13
philip1209 wrote: post #4

Earlier quoted context omitted.

Doesn't look like it: dig +short NS github.io ns2.p16.dynect.net. ns4.p16.dynect.net. ns1.p16.dynect.net. ns3.p16.dynect.net.

All that shows is who they're hosting their DNS with, it has nothing to do with using a CDN. Dynect offers a CDN management tool that makes it easy to balance multiple CDNs across specific regions, so I'm not at all surprised they're using them for their DNS.

If they were using Cloudflare, as the other commenter had asked, they would be using Cloudflare nameservers

Re: Faster, More Awesome GitHub Pages

#19

Post by roozbeh18 »

harryh wrote: post #12

What's an ALIAS record? I don't even see that here: https://en.wikipedia.org/wiki/List_of_DNS_record_types

You can not have a CNAME at apex/root/naked domain such as example.com level. you can not point example.com CNAME username.github.io. The DNS spec only allows A records/Ip Addresses at this level. some companies have come up with Alias record which works like CNAME on apex domain, some old DNS Servers might not recognize this but most do these days.

Re: Faster, More Awesome GitHub Pages

#20

Post by namecast »

chc wrote: post #15
harryh wrote: post #12

What's an ALIAS record? I don't even see that here: https://en.wikipedia.org/wiki/List_of_DNS_record_types

To my understanding, it's a new, nonstandard thing invented by DNSimple that lets you specify your base domain as a reference to another domain — basically, it's like a CNAME where an A record would normally be required.

Yep. ALIAS records exist basically to get around the CNAME restriction introduced in RFC 1034. Basically, with a CNAME, you can't have any other qtypes for the leaf that you're on. (I'll explain what that means...)

For example:

If you set up subdomain.yourdomain.com to be an A record to to 10.0.1.1, you can also set up additional A records, AAAA records for IPv6, and even MX and NS records for subdomain.yourdomain.com.

If you set up subdomain.yourdomain.com to be a CNAME, you can't have any other record types for subdomain.yourdomain.com.

ALIAS records exist because you can't CNAME your root record - the root of your domain has to have at the very least an SOA record, and NS records are going to be needed for the domain to actually resolve. Since those record types exist at the root of your domain, and since CNAME's can't coexist with other record types, you can't use CNAME's at the root of your domain.

Accordingly, the ALIAS record really is only useful to redirect the root apex of your domain somewhere else.

(Just my two cents.)

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